Biodegradation and in vitro cytocompatibility of Mg–0.4Zr alloy processed by extrusion and equal channel angular pressing

The impact of the equal channel angular pressing on the mechanical properties, corrosion behavior and cell viability of extruded Mg–0.4Zr alloy was examined. Microstructural analyses showed that 1, 2, and 4 ECAP passes respectively decreased the grain size from 8.3 μm to 7.5, 2.6, and 2.2 μm, due to dynamic recrystallization. Textural analysis revealed the gradual transformation of the extrusion-induced fiber texture into a shear texture during ECAP. The ultimate shear strength decreased after 7 days immersion in the phosphate-buffered saline (PBS) solution. The 2-pass ECAP sample showed the highest strength of 106.6 MPa after immersion among all test conditions. The hydrogen evolution test results conducted in PBS solution for 250 h indicated that ECAP enhances corrosion resistance with the lowest corrosion rate of 0.19 mm/year in the 2-pass sample. It is because of the finer grain size, the presence of smaller secondary phase particles distributed more uniformly, as well as more stable crystallographic planes exposed to the PBS solution. Electrochemical corrosion tests also confirmed that the 2-pass sample offers greater resistance to corrosion. The findings of the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay on osteoblast-like cells cultured on the extruded and 2-pass samples indicated an absence of cytotoxicity, with viabilities of above 80%. At each time point assessed, there was no notable difference in cell viability between the two groups and cells maintained high metabolic activity throughout the culture period. Moreover, the 2-pass sample exhibited improvements in cellular attachment and morphology.